Stents are well known in the art. U.S. Patent Publication No. 2006/0122694 A1, for example, discloses a stent which comprises an essentially tubular open supporting structure of interconnected webs. This supporting structure is radially distensible with deformation of the webs formed by interconnected trusses in sections for application of the stent in a blood vessel in a patient.
With the previously known stent, predetermined breaking points are also integrated into the supporting structure, serving to fragment the stent after application. As mentioned in the U.S. patent publication cited above, this fragmentation serves to break apart the electrically conductive conductor loop formed by the peripheral trusses to thereby increase the visibility of the body material in the lumen surrounded by the stent in a magnetic resonance examination. Since the integrity of the webs is still guaranteed during application of the stent, this stent has enough stability to ensure the desired vasodilation through its application.
With the known stent, the predetermined breaking points are formed by bridges of material within the stent webs made of a material having a greater corrodability. As an alternative to this, the predetermined breaking points may be formed by a cross-sectional constriction which leads to a defined dissolution of the structural stability of the stent in the area of the predetermined breaking point due to the corrosion of the stent that occurs there.
The more recent development in the field of stents provides for the use of magnesium and its alloys as the materials. These materials are biodegradable and thus lead to the desired dissolution of the stent after widening the blood vessel and its inherent stabilization. This prevents the problem whereby the stent, acting as a foreign body, tends to an accumulation of cells over a period of time, and therefore the treated blood vessel becomes occluded by a restenosis.
Magnesium and its alloys are, however, at risk of breakage under corrosive stress and/or vibrating stress at the same time, such as that to which a stent administered in a pulsating bloodstream is exposed. In addition, local spots of corrosion may occur, e.g., due to irregularities in the material or the surface. Stents such as those known from European Patent Application No. 1 430 854 A1, for example, may thus be subject to the risk of uncontrolled fragmentation after initial deformation for radial widening of the stent so that the supportive function of such a stent is at risk, in particular, in the arterial blood vessels. The reason for this is that individual web elements in the area of uncontrolled fragmentation no longer have a structural mechanical cohesion and the supportive function of the stents is lost with an increasing number of fragments formed.